First, I hope you are experiencing some respite from the ugliness of your situation and are able to enjoy a peaceful holiday break with your family.
Proserpina is correct that you can do little about what is said in court proceedings. There is an absolute privilege that attaches to these words that protects against any defamation action arising from what is said, no matter how false or injurious the claims may be. It is up to the state to decide if perjury charges will be pursued against a person who lies under oath, and the state rarely takes this action (due to the difficulty in obtaining the proofs necessary for a successful case and due to the expense involved).
Generally, however, the court is well-aware that much of what is said by parties in, especially, child support and divorce and related hearings will be bending the truth a bit (or a lot). In Alabama, for instance, most of the juvenile and family court judges and referees have over 7 years of experience handling these cases. They are not blind to the false claims often made by battling ex-spouses in court. The court takes all of this into consideration when making a decision and will not place any more weight on what is said than it deserves (ie. than what is supported by evidence).
The fact that you cannot seek legal recourse through a defamation suit filed against your defamer for what he says in court, however, does not mean that you are entirely without recourse.
Since the Mondale Act was passed in 1974 (refer to US Code Title 42, Chapter 67), there have been recognized abuses of this Child Abuse Prevention Act. It has been amended several times since '74, in fact, to address some of the major ones that have been evidenced. The Act in its amended form was reauthorized in 2003. What the Act does, in part, is makes the reporting and handling of suspected child abuse and neglect mandatory. It also makes child service evaluators subject to jail time for inadequate investigating of the reports that are made. This has been shown to have saved many children from abuse and neglect in the years since the Act has been in effect, which is good. That was its intent.
The investigations include interviews with the child(ren) in question, criminal background checks of those involved, a review of medical and/or psych records, interviews with those who may have knowledge of situation reported, home visits, etc. The law requires that the reports made to CPS (and the name of the person making the initial report) remain confidential. Only information deemed necessary to protect the welfare of the child(ren) will be released, and only to those with an absolute need to know.
However, if you are having to handle several false reports made about you (and this, by the way, is the area where the majority of problems have arisen with the passage of the Act in 1974), you should contact your local law enforcement agency and file a complaint (against a "John Doe reporter" if the reporter is unknown) every time you are the subject of a CPS investigation.
It is illegal to intentionally file a knowingly false police or CPS report. These reports are covered by a qualified privilege, not the absolute privilege which covers the words communicated in court or in reference to court proceedings. These reports, in other words, can spawn a legal action if it can be proved that the reports were made with "actual malice." Although it is often impossible to prove that a report was made by a person who knew it was false at the time it was made, and that it was made by this person with a malicious intent to cause harm, having a police record of complaints can be useful as an additional official record of investigations conducted by CPS. Eventually you may be able to use these records to support, at the very least, an harassment complaint against the reporter.
In addition to filing police complaints, if you disagree with or have problems with any report that is made by a CPS evaluator, you can discuss this directly with the evaluator assigned to your case. If you cannot get what you are seeking from the evaluator, you can move from the evaluator to the evaluator's supervisor. Finally, if you are continuing to be investigated based on false reports filed with CPS and you are unable to get any relief through your contact with the evaluator and supervisor, you can request an administrative review by the DHS.
You can also request that your name and identifying information be removed from all case records, if a court has found that the information provided in the initial report(s) was unfounded and CPS could not substantiate any of the claims after their investigation into the matter.
I have reviewed briefly your posting history on this forum, moldableman, and it appears you have had in recent years several struggles with the biological father of your step-daughter. If all of the adults in this child's life are not in counseling to resolve their differences, they should be. Otherwise this child will have major issues of her own to deal with, and that all of you will have to manage, when she reaches teenagehood and adulthood.
Good luck.
